Genicanthus lamarck: An Elegant, Reef-Safe Angelfish

Male Lamarck's Angelfish (Genicanthus lamarck)

Male Lamarck’s Angelfish (Genicanthus lamarck)

Owing to the natural tendency of many species to nip at or outright consume sessile invertebrates, angelfishes are often of dubious suitability when it comes to their inclusion in reef aquariums. However, at least one angelfish—Lamarck’s angel (Genicanthus lamarck)—is generally very well behaved in reef systems and quite attractive to boot.

Physical traits

G. lamarck reaches about 9 inches in total length and possesses the lyre-shaped tail typical of its genus (the common name “swallow-tail angels” is often ascribed to Genicanthus species). While not the most chromatically gifted of the angels, it’s quite attractively patterned nonetheless. Also, adults of this species exhibit sexual dichromatism—distinct color differences between the sexes.

G. lamarck is a protogynous hermaphrodite making it capable of transforming from female to male, which this specimen is doing.

G. lamarck is a protogynous hermaphrodite making it capable of transforming from female to male, which this specimen is doing.

Both genders are grayish-white overall with black, horizontal stripes on their flanks; a black band running just below the top edge of the dorsal fin; and small black dots on the tail, anal fin, and rear of the dorsal fin. However, they differ in that the black dorsal band and the top horizontal stripe are much more pronounced on the female, the female has black on the top and bottom edges of the tail while the male does not, and the male’s pelvic fins are black while the female’s are grayish-white.


Unlike most other angels, G. lamarck feeds on plankton in open water, hence its disinterest in nipping at sessile invertebrates. In aquaria, this angel should be offered a combination of various small, meaty foods—e.g., mysids, chopped mollusk and crustacean meat, etc.—and algae-based items. As with all planktivores, G. lamarck requires several small daily feedings rather than a single large meal.


As noted above, G. Lamarck can reach a respectable 9 inches in total length. Add to that its relatively high activity level and need for open swimming space, and you can probably guess it needs a decent-sized aquarium. I wouldn’t go much smaller than 125 gallons, especially if you plan to keep more than one specimen.


This is a relatively peaceful angelfish that won’t bother most other fishes, with the possible exception of direct food competitors (i.e., other planktivores) that are small and passive enough to bully. In larger systems, Lamarck’s angels can be kept in pairs or groups containing only one male. Of course, it’s also among the best angelfishes—if not the best angel—for sufficiently sized reef systems.


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About Jeff Kurtz

Jeff Kurtz is the Co-founder/Editor of Saltwater Smarts, former Senior Consulting Editor for Tropical Fish Hobbyist Magazine, and the aquarist formerly known as “The Salt Creep.” He has been an aquarium hobbyist for over 30 years and is an avid scuba diver.


  1. The picture used of the female Lamarck is incorrect. That is a female that almost completed the changing into male transformation, one that just turned into a male. In younger females the thick black band extends and curves down to the lower part of the tail.

    • Jeff Kurtz says

      Ah! I think you may be right, Riaan! Looks like we ran an image of one in transition. I probably should also have mentioned in the post that G. lamarck is a protogynous hermaphrodite and, thus, capable of making said transformation from female to male.

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